Many modern fuel injectors use solenoids to move a spool valve or poppet valve located within the fuel injector into an open position, which allows a working fluid, such as oil, to flow into an intensifier chamber and compress fuel within a high-pressure chamber. The compressed fuel is then injected into the combustion chamber of the engine. During this process, fuel injectors experience tremendous forces. These forces result from a variety of sources, including the activation of the solenoids, high-pressure mixing and injection of reagents into the cylinder, and the rapid combustion of gases within the cylinder.
As will be described in more detail below, these forces can cause metal fatigue at various points on the fuel injector and result in failure or reduced performance of the fuel injector.